Choke mechanism for firearms



June 2, 1959 A. Y. GRAHN 9 7 CHOKE MECHANISM FOR FIREARMS Filed April 26, 1956 IN VENTOR MX'W } A'ITORNEYS United States 8*Claims. (or. 42-79 This invention relatesto'a choke mechanism for firearms, and more particularly shotguns,.and relates especially to an automatically adjustable choke mechanism whereby adjustment is made in the amount of choking to whichzthebarrel is subjected in response tothe firing or-dis'charge of the gun.

Adjustable choke mechanisms forfirearms have long been: known and also automatically adjustable choke mechanismshave been'proposed, such mechanisms usually; comprising a split orslotted choke tube which is attached to the gun barrel anda relatively movablesleeve surrounding the choke tube and adapted to constrict it when moved upon the tube. Usually the arrangement is such thattheconstricting tube is moved in some manner in response to the firing of the gun so tha't automatic adjustment ofthe amount or-degree of choke will be effected.

An-t automatically adjustable choke mechanism has a distinctadvantage over a manually adjustabletype in that very; often a hunter will be able to getmore than oneshot at game after it has been flushed. Usually the first shot will-be made when the game is relatively close and no choking action or relatively little choking action is required. At the next shot the game will-beat a greater distance from-the gun andacloser pattern-will be desirable. The same istrue ifathird sh'ot is-secured.- If these adjustments fromone choking position to anoth'er may beautornatically eiiected-bythefiring-f the gun, the result describedabove may; be obtainedwhere it would not be possible to adjust the choke manually between the. consecutive discharges of the firearm without the gamegetting out of range.

All of the adjustable choke mechanisms heretofore madeemploy a slotted or*constrictable tube in-one form or anothertogether with a relatively movable outer sleeve tosefiect restriction of the slotted choke tube; In the present instance, however, an effective choking operationis obtained by means of aninexpansible choke tube Whichis of constant diameter and is of substantially uniform diameter except adjacent its rear end' where it receives the chargeaof shot from the muzzle end of the gun... Thediameter of the choke tube is substantially that of the gun barrel, and choking action is obtained by varying..the distanceof this tube from the muzzle end of the u For example, it has been found that when the inlet end of the choke tube is close to the muzzle of the gun, substantially an open pattern is'the result, that is say, the same pattern which would be obtained without the use oflany choke mechanism. However, When the choke tube is advanced a certain extent, say a half inch, a degree of choking action is obtained while, if the choke tube is further advanced so that its entrance end is, for example, substantially an inch from the muzzle end of the gun barrel, substantially a full choking'effect is obtained.

By making use of this principle and by providing a choke. tube of constant bore which may be moved forwardly by discharge of the gun and which is releasably held in various adjusted positions so that itmoves forwardly in a step-by-step manner-one step at each discharge of the guna reliable and eflicient automaticaL 1y adjustable choking mechanism is obtained.

One object of the present invention is to providean automatically adjustable choke mechanism-which will be positive and reliable in operation and economical to manufacture.

A'further object of the invention is to' provide an automatically adjustable choke mechanism whereinra choketube of constant diameterthat is one which is not expansible or constrictable-will be mounted in front of the gun barrel for movement axially thereof, and the movement of the tube will be-effected in response todischarge of the gun.

Still another object of the invention is to provide achoke mechanism of the character described above wherein means will be provided for releasably holding the choke tube in adjusted positions'sothat it will-move for wardly in astep-by-step manner upon discharge of the gun.

. A still further object of the invention is the provision of an automatically adjustable choke mechanism 'of'the character described-wherein the choke tube is moved in a 'stepby-step manner andspaced means are provided upon cooperating parts-of the mechanism to'prevent the tube from moving through-a distance of-"more than one step upon a single discharge otthe gun.

To these and other ends the invention consists in the novel features'and combinations of parts to be hereinafter described and claimed;

In the accompanying drawings:

Fig. 1 is-aside elevational viewof the muzzleend of a gun barrel having theinvention applied thereto;

Fig. 2 is an'enlarged sectional view'on line 2-2 of Fig. 1, showing the choke mechanism in open bore position;

Fig. 3 is-a view similar to Fig. 2 showing the parts in full-choke position;

Fig. 4'is-a sectional-view ondine 44 of'Fig. 2; and

Fig. 5 is anelevationalview of the friction ring employedto' releasably holdthe choke tube inany given adjusted position.

To illustrate an embodiment of'the invention there is shown in the drawings the" muzzle end of a gun barrel lit-having secured thereto 'by brazing or equivalent means an adapter-'11. Adjacent the forward end thereof theadapter is provided-with external screw threads 12-and. a a cylindrical sleevermember- 13'- is provided with internal threads lid-adjacent its rear end so thatit may be threadedly secured to the adapter:

As shown more especially'in-Fig. 2, the internal diameter of the. sleeve 'or'cylinder member 13 is somewhat greater than the bore 15 of the gun barrel; and this member is provided with'an internalannular projection or rib 16 a shortdistance from its front end- Adjacent the front end of this member is an internal flange 17 having a rearwardl-y facing beveledsurface 18. The arrangement is. such that an-annular recess- 19 is providedbetween the flange17 and the internal projection or rib 16 Slidably mounted -within-thesleeve member 13 is atubular choke.member20, this.--member, as indicated in Fig. 4, beingcircumferentially'continuous.in thatitis not provided with longitudinal'slots as is usually the case in adjustable choke mechanisms; Therefore,-this tube isofconstant diameter in the sense that its-diameter atrany point is'notchanged by constriction or-expansion during its operation. Moreover, its. diameterover the greater portion of its length is: substantiallythe same as 'thatof theborelS- of the gun barrel.. At the-rear or entranceend of the choke tube, however, the -inner wall is flared as shown at 21 so as to provide a flaring or funnel-shaped portion to receive the charge of shot from the muzzle end of the gun, It will be appreciated that as the rear end of this choke tube isslightly spaced away a distance of of an inch or more, from the end of the gun barrel, the charge will probably expand slightly before it reaches the tube. 'This flaring portion 21 of the choke tube will recollect the shot and direct it into the portion of the tube of uniform diameter.

Surrounding the choke tube 20 and located within the annular recess 19 is a split ring 23, the width of the ring being substantially that of the recess 19. This ring is held against appreciable movement in the recess by contact of its abrupt rear edge with the abrupt forward edge 24 of the rib 16. At its forward edge the ring 23 is beveled, as shown at 25, to cooperate with the beveled face 18 of the flange 17.

' This split ring 23 fits with a suitable amount of friction about the outside diameter of the choke tube 20 and, as the ring is held against axial movement within the cylinder member 13, it will exert friction upon the tubular member to tend to inhibit relative movement between the choke tube and the cylinder member 13. When the choke tube is moved forwardly by the discharge of the gun, as will be hereinafter referred to, there will be a tendency for the ring 23 to be moved forwardly and the contact of the beveled surface 25 of the ring with the beveled surface 18 of the flange 17 of the sleeve member 13 will tend to constrict the ring about the choke tube so as to exert the required friction upon the latter.

It is desired that the choke tube not be moved throughmay be externally threaded, as shown at 35, and the outer sleeve may be internally threaded, as shown at 36, so that the latter may by rotation thereof be secured to the inner sleeve 13 and thus prevent movement of the choke tube upon discharge of the gun.

With the parts in the open-bore position shown in Fig. 2 and the threads 35 and 36 disengaged, the choke mechanism will respond to the discharge of the gun and the choke tube will be adjustedforwardly in a step-bystep manner. If, for example, the gun is fired with the parts in position shown in Fig. 2, the effect of the discharge, probably due to the recollecting of the shot charge by the flared portion 21 of the choke tube 20, will impart forward motion to the latter and cause the'shoulder 29 of the forward internal groove of the sleeve 26 to jump past the ring 33. As shown, however, as this sleeve 26 reaches 7 a position wherein the ring is opposite the intermediate one of these internal grooves, it will expand into this out its full range of movement by a single discharge of d the gun but that it move in a step-bystep manner, and to this end means are provided to releasably hold the choke tube at various positions of adjustment axially of'the gun barrel. For this purpose an outer cylinder member or sleeve 26 embraces the inner sleeve 13. This outer sleeve is provided with a forward flange 27 threadedly secured at 28 to the forward end of the choke sleeve 20 so that the outer sleeve and choke sleeve will move together.

The outer sleeve 26 is also provided with a plurality of annular grooves or recesses, these grooves having relatively abrupt rear end faces 29 and gradually and forwardly sloping peripheral surfaces 30. As shown, three of such grooves or recesses are provided interiorly of the sleeve 26, but it will be understood as many will be provided as will be required according to the number of choke positions desired. The wall of the inner sleeve 13 is provided with an external annular recess 32 Within which is mounted a split ring 33 (Figs. 2 and 5). This recess may be provided opposite the internal rib 16 as more metal is present at this point for that purpose. This ring is adapted to seat in one of the annular internal recesses on the sleeve 26 in order to releasably hold the sleeve in adjusted positions and, therefore, releasably hold the choke tube in adjusted positions.

It will be appreciated that the split ring 33 olfers a certain amount of frictional resistance to the movement of the choke tube with respectto the inner sleeve 13 but, as this is not usually suflicient, I prefer to provide the friction ring 23 in addition to the holding ring 33. It is possible, however, that the ring 33 may be employed to perform both the frictionally restraining function and the releasably holding function and that, therefore, both of these functions may be accomplished by the same means, and the invention is, therefore, not limited to separate means for both frictionally restraining the forward movement of the choke sleeve and releasably holding it in its various adjusted positions.

Indicia indicated at 34 may be provided upon the exterior portion of the inner sleeve 13 to indicate the position of the outer sleeve 26 and, therefore, the position of the choke tube so as to advise the user as to the particular adjustment of the choke tube at any time. While three adjustments or positions are shown in the drawing, it will groove, ride up the flaring surface 30 thereof, lodge against the shoulder 29 of this groove, and releasably hold the outer sleeve and choke tube in this position for the next discharge of the gun.

If the gun is again discharged, the same action will take place and the outer sleeve 26, together with the choke tube 20, will move forwardly another step until the split ring 33 occupies the rearmost of the internal annular grooves in the outer sleeve 26. This is the position shown in Fig. 3 wherein the choke tube is at the forward limit of its movement and. the parts are in full-choking position or the maximum choke position permitted by the structure shown.

The choke tube 20 is provided adjacent its rear end with an external shoulder 38 which is adapted in the most forward position of the tube to abut the rear shoulder 39 of the rib 16 so as to prevent complete detachment of the parts if the gun is fired when the choke tube is in the position shown in Fig. 3.

It will also be understood that, if the choke tube is made of larger or smaller diameter, a greater or lesser choking eflect will be effected in each position thereof so that while the internal bore of this tube is substantially that of the gun, it may vary to some extent one way or the other, depending upon the amount of choke desired for each position of the tube. Additionally, it will be understood that, if desired, the choke tube 20 may be made somewhat longer and more positions of adjustment obtained so that all ranges of choke usually found in the manually adjusted chokes would be covered.

While I have shown and described one embodiment of my invention, it will be understood that it is not to be limited to all of the details shown, but is capable of modification and variation within the spirit of the invention and within the scope of the claims.

What I claim is:

1. A choke mechanism for attachment to the muzzle end of the barrel of a gun comprising an inner sleeve member adapted to be attached to the end of the barrel, a choke tube having a circumferentially continuous wall slidably mounted within said sleeve member, an outer sleeve member embracing the inner sleeve member and projecting beyond the latter and having its forward end secured to the forward end of the choke tube, cooperating interengaging means carried by said sleeve members releasably holding the outer member and choke tube in various adjusted positions axially of the inner sleeve member, and said choke tube having an internal bore substantially equal to the bore of the gun barrel for the greater part of its length but having a flaring portion adjacent its rear end.

2. A choke mechanism for attachment to the muzzle end of the barrel of a gun comprising an inner sleeve member adapted to be attached to the end of the barrel, a choke tube having a circumferentially continuous wall slidably mounted within said sleeve member, an outer sleeve member embracing the inner sleeve member and projecting beyond the latter and having its forward end secured to the forward end of the choke tube, cooperating interengaging means carried by said sleeve members releasably holding the outer member and choke tube in various adjusted positions axially of the inner sleeve member, said means comprising a split ring carried by one of said members and frictionally engaging the other thereof, and said other member being provided with spaced annular recesses in which a portion of said ring is received.

3. A choke mechanism for attachment to the muzzle end of the barrel of a gun comprising an inner sleeve member adapted to be attached to the end of the barrel, a choke tube having a circumferentially continuous wall slidably mounted within said sleeve member, an outer sleeve member embracing the inner sleeve member and projecting beyond the latter and having its forward end secured to the forward end of the choke tube, cooperating interengaging means carried by said sleeve members releasably holding the outer member and choke tube in various adjusted positions axially of the inner sleeve member, and a split ring member embracing the outer surface of the choke tube and disposed between it and the inner surface of the inner sleeve to frictionally restrain movement of the choke tube.

4. A choke mechanism for attachment to the muzzle end of the barrel of a gun comprising an inner sleeve member adapted to be attached to the end of the barrel, a choke tube having a circumferentially continuous wall slidably mounted within said sleeve member, an outer sleeve member embracing the inner sleeve member and projecting beyond the latter and having its forward end secured to the forward end of the choke tube, cooperating interengaging means carried by said sleeve members releasably holding the outer member and choke tube in various adjusted positions axially of the inner sleeve member, said means comprising a split ring carried by said inner sleeve and held against movement axially thereof, said outer sleeve having internal annular recesses to receive a portion of said ring, and additional means to frictionally restrain movement of said choke tube in the inner sleeve comprising a split ring embracing the choke tube, and the wall of said inner sleeve being provided with an internal annular recess to receive said ring and hold it against axial movement.

5. A choke mechanism for a shotgun or the like comprising an inner sleeve adapted to be secured to the muzzle end of the gun barrel, an outer sleeve slidably and telescopingly embracing the inner sleeve, means to hold said outer sleeve in various adjusted positions axially of the inner sleeve, and a choke tube secured at its forward end to the forward end of the outer sleeve and slidably received within the inner sleeve, said choke tube when in its innermost position within the inner sleeve extending to a point adjacent the muzzle end of the gun barrel, the Wall of said choke tube being circumferentially continuous and the bore thereof being substantially equal to that of the gun barrel for the greater part of its length but being flared outwardly adjacent its rear end.

6. A choke mechanism for a shotgun or the like comprising an inner sleeve adapted to be secured to the muzzle end of the gun barrel, an outer sleeve slidably and telescopingly embracing the inner sleeve, means to hold said outer sleeve in various adjusted positions axially of the inner sleeve, a choke tube secured at its forward end to the forward end of the outer sleeve and slidably received within the inner sleeve, said choke tube when in its innermost position within the inner sleeve extending to a point adjacent the muzzle end of the gun barrel, the wall of said choke tube being circumferentially continuous and the bore thereof being substantially equal to that of the gun barrel for the greater part of its length but being flared outwardly adjacent its rear end, and means to secure said outer sleeve to said inner sleeve to prevent relative movement between the two sleeves when desired.

7. A choke mechanism for attachment to the muzzle end of the barrel of a gun comprising an inner sleeve member adapted to be attached to the end of the barrel, a choke tube having a circumferentially continuous wall slidably mounted within said sleeve member, an outer sleeve member embracing the inner sleeve member and projecting beyond the latter and having its forward end secured to the forward end of the choke tube, and cooperating interengaging means carried by said sleeve members releasably holding the outer member and choke tube in various adjusted positions axially of the inner sleeve member.

8. An automatically actuated choke mechanism for attachment to the muzzle end of the barrel of a gun comprising a sleeve member adapted to be fixedly attached to the end of the barrel, an inexp-ansible choke tube slidably mounted within said sleeve member, means frictionally restraining movement of said choke tube relatively to the sleeve member and releasably holding it in various adjusted positions with respect to the sleeve member, said frictional restraining means comprising a member secured to said choke tube and extending over said sleeve and having a plurality of spaced recesses therein and means carried by said sleeve member and projecting therefrom to engage in said recesses, the outer wall of each of said recesses being inclined with respect to the axis of the tube.

References Cited in the file of this patent UNITED STATES PATENTS 1,892,522 White Dec. 27, 1932 2,428,232 Limon Sept. 30, 1947 2,484,988 Finlay Oct. 18, 1949 2,676,429 Gotterson Apr. 27, 1954 2,779,119 Fawcett .....l Ian. 29, 1957 

